Treating ferrous metals with aluminum



Patented Sept. 2, 1952 TREATING FERROUS ALUlWIN METALS WITH Guy E. McKinney and Paul J. Motter,

' Canton, Ohio No Drawing. Application January 5, 1951, Serial No. 204,677 a 12 Claims. 1 v

The invention relates generally to a novel process for treating ferrous metals with aluminum,

and more particularly to a process of treating iron or steel with aluminum to produce a product having improved characteristics.

Pure aluminum oxidizes rapidly when heated in air or in the presence of oxygen, to the extent that aluminum powder possesses high explosibility. Hence, while it is customary to add alu-.

minum to molten steel to de-oxidize the FeO in the steel and to refine .the grain size, it is very difficult to add the aluminum without high oxidation losses of the aluminum. Many different methods have been tried of adding the aluminum to molten ferrous metal in the ladle and in the mold,"but is is still common practice to add metallic aluminum by throwing it byhand into the ladle while it is being filled with molten metal.

These prior methods accomplish good resultsinsofar as attaining de-oxidation and grain refinement of the steel, but there is virtually no metallic aluminum remaining in the final product.

Consequently, in alloying aluminum-with iron or steel, the aluminum is often first alloyed with one or more other metals such'as silicon and manganese.

Iron-aluminum alloys have high heat resistance at elevated temperatures, and also have high corrosion resistance. Also, aluminum improves the magnetic properties of iron and steel, and iron-aluminum alloys have increased electrical resistivity, while desirably possessing substanti'ah ly more ductility than other alloys having similar characteristics, such as iron-silicon. However, according to the Metals Handbook, 1948 edition, page 605, aluminum has" never become a serious competitor of silicon in this latter field because of difficulties encountered in the known manufacturing processes.

We have discovered a novel process by which aluminum canbe alloyed easily with iron or steel in sufficient proportions to change and improve the characteristics of the ferrous metal.

Itis a general object of the present invention combining alumi to provide a novel process of num with ferrous metals.

Another object is to provide a novel process of producing an iron-aluminum alloy having im-' proved characteristics. 7

Another object is to provide a novel process of alloying aluminum and ferrous metals, which-is economical and easily performed without requiring special care or skill; 4

'A further object is to provide anovel process of alloying aluminum and ferrous metals, which produces free hydrogen as a by-product.

2 A still further object is toprovide a novel proc ess of treating iron with aluminum which process may, if desired, be modified for the purpose-of producing substantially pure iron.

These and other objects are accomplished by the novel methods comprising the present invention, preferred embodiments of which are set forth by way of example in the following specification, the scope of the invention being defined in the appended claims forming part hereof.

I Our novel process is performed in two stages;. the first stage prepares the aluminum for the alloying step, and the second stage consists of the actual alloying of the prepared aluminum. with" the ferrous metal in a molten or highly heatedcondition. a

tube, and the temperature is held at 2200 F.

In the first stage we pnlverize pure aluminum and mix it with pulverized fire clay, for subse quent alloying with ferrous metals. While the composition of the clay may vary somewhat, we prefer to use a clay known as semi-fire clay having the following approximate analysis:

Percent Silica (SiOz) 57.22, Alumina (A1203) 25.19 Iron oxide (F6203) 5.59 Calcium oxide (CaO) .70

Magnesium oxide (MgO) 1.86 Balance moisture. a

The clay is first dried and then pulverized to a fine texture, after whichit is covered over the pure powdered aluminum in a container. a closed or an open container may be used, depending upon whether it is desired to produce free hydrogen as a by-product.

If production of hydrogen is desired, the pure pulverized aluminum is first mixed with the pulverized fire clay in the proportion of about three parts aluminum to one part clay by volume, and

this mixture is placed in the bottom of a closed container or retort having a vent tube in its upper portion. The-mixture is then completely covered and blanketed with more of the pulverized fire clay, and the total amount of clay in the covering may be four to five times that of the mixture of pulverized aluminum and clay by volume. The container is then heated to bring the charge up to a temperature between 2000 F. and 2200 F., and is held at that temperature for about thirty minutes. The container is allowed to cool for about fifteen minutes, and then is re-heated to 2200 F.

During this heating operation large quantitiesof free hydrogen are given off through the vent Either 3 during the second heating operation until the free hydrogen is exhausted. We make no attempt to explain the production of hydrogen, except to say that we have performed this process as described herein, and have actually produced large quantities of free hydrogen.

If it is not desired to collect hydrogen as a by-product, the pulverized aluminum may be mixed with the pulverized clay in the proportions of three parts aluminum to one part clay by-Volume, and this mixture placed in the bottom of an open container such as a crucible.

The mixture is then completely covered with more of the pulverized clay, and the amount of additional clay may be four to five times that of the mixture by volume. In this case, it is 168- sential that the aluminum be completely blahketed so as to exclude all air therefrom during the heating operation.

The blanketed mixture in the open container is 'heatedlin the same wayas in theclosed container, that is, brought up to a temperature of '2000-2200 F., held at that temperature for about thirty minutes, allowed to cool for about :fifteen minutes,and then re-heated to 2200 F.

until all of the hydrogen is exhausted.

After the charge in either'the open or closed container has been cooled the aluminum is in the form of a porous light-green colored amass which contains aluminum oxide, and about 54% of actire aluminum, as shown by analysis. This mass is separated from any residual .clay, and then pulverized to a fine powder. This powdered aluminum compound may be added to iron or steel in a molten or highly heated condition, preferably -to-the-molten ferrous metal in a ladle.

The addition ,of the powdered aluminumcompound .to the molten iron or steel causes a mild boiling action for a few seconds, which is .probably due to the action of the aluminum as a flux or scavenger. If the aluminum compound is added to the molten metal in a ladle, the metal may be safely poured within a few seconds after this mild boiling action has terminated.

The proportion of the powdered aluminum compound to be added to the molten metal varies considerably depending upon the analysis of the molten metal and the impurities present therein. However, exact proportions are not required and the amount of the prepared aluminum compound added may be varied substantially without affecting the process excepting to change the amount of aluminum present in the final product.

.As an example, by making an addition of the powdered aluminum compound in a ladle of ordinary foundry iron in the proportion of about 2 parts aluminum compound by weight to 90 parts by weight of iron, we have obtained cast iron containing 0.26% aluminum by analysis.

If the powdered aluminum compound is added in a furnace, it is firstspread in a layer over the bpttomof a preferably'electric furnace and then iron to be melted is added on top of said layer. The proportions of the powdered aluminum compound and iron in the form of pig iron or scrap or both may vary considerably. The charge is then brought up to-the melting temperature of the iron, and the clay in the powdered aluminum compound rises to thetop and forms a skin over the molten metal.

This charge is held at this temperature until the skin on top is completely quiescent, which may be a period of about fifteen minutes and the molten metal is then poured. Where the powdere alumi m com nd constituted 1 Part by weight to 8 parts by weight of iron, we have obtained iron containing .96% aluminum. On the other hand, we have obtained iron containing as much as 9.63% aluminum by increasing the proportion of powdered aluminum compound to iron.

Iron alloyed with aluminum in accordance with our novel process in proportions of the order of the foregoing example, produces a prod- .uct which has high heat resistance and corrosion resistance of the order of stainless steel. The product will take a brilliant polish and can be used in making water pipe and containers such as boilers and radiators. Moreover, the product can bereheated again and again with outloss of iron. Iron-aluminum alloys can be produced by this process for use as heat-resisting alloys, and as ductile alloys having improved magnetic properties and increased electrical resistivity.

If a substantially pure iron is desired, it is only necessary to :modify the process by prolonging thexheatlng period. For example, starting with a layer in the electric furnace of 3 parts by weight powdered aluminum compound and 8 partsby weight of iron on top and bringing the charge'up to the melting temperature of iron, if the charge is held at that temperature for about 30 minutes instead of fifteen, iron of 96.29% purity with only a trace of aluminum is obtained. If the charge is held at said melting temperature for about 45 to 60 minutes, iron of 99.69% purity is obtained.

In the foregoing description, certain terms have been used for brevity, clea-rness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the art, because such words are used for descriptive purposes herein and are intended to b broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details set forth.

Having now described the invention, the manner of operation and uses of preferred embodiments thereof, and the advantageous new and usefulresults obtained thereby; the new and useful methods andproducts, and reasonable equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

We claim:

1. The process of combining aluminum with ferrous metal, which consists in covering pulverized pure aluminum with fire clay and heating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, and then adding .thepulverized aluminum mass to the ferrous metal in a highly heated condition.

2. The process of combining aluminum with ferrous metal, which consists in mixing pure aluminum with a lesser amount of fire clay, covering the mixture with additional fire clay and heating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same. and then adding the pulverized aluminum mass to the ferrous metal in a highly heated condition.

3. The process of combining aluminum with ferrous metal, which consists in covering pulverized pure aluminum with fire clay, heating the covered aluminum to a temperature of 2000 F. to 2200 F. for about 30.minutes, allowing the temperature to drop for about 15 minutes, reheating to a temperature of 2000 F. to 2200 F., cooling and Separating the resulting aluminum mass and pulverizing the same-and then adding the pulverized aluminum mass to ferrous metal in a highly heated condition.

4. The process of combining aluminum with ferrous metal which consists in mixing pure aluminum with a lesser amount of fire clay, covering the mixture with additional fire clay and heating to a temperature of 2000 F. to 2200 F. for about 30 minutes, allowing the temperature to drop for about 15 minutes, reheating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, and then adding the pulverized aluminum mass to ferrous metal in a highly heated condition.

5. The process of combining aluminum with ferrous metal, which consists in covering pulverized pure aluminum with fire clay in the proportions of about four to five parts by volume of clay to one part of aluminum and heating to a temperature of 2000 to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, and then adding the pulverized aluminum mass to the ferrous metal in a highly heated condition.

6. The process of combining aluminum with ferrous metal, which consists in covering pure aluminum with fire clay in the proportions of about four to five parts by volume of clay to one part of aluminum, heating the covered aluminum to a temperature of 2000 F. to 2200 F. for about 30 minutes, allowing the temperature to drop for about 15 minutes, reheating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, and then adding the pulverized aluminum mass to ferrous metal in a highly heated condition.

7. The process of combining aluminum with ferrous metal, which consists in mixing pulverized pure aluminum with fire clay in the proportions of about three parts aluminum to one part clay by volume, covering said mixture with additional clay in the proportions of four to five parts of clay by volume to one part of the mixture, heating the covered mixture to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, and then adding the pulverized aluminum mass to the ferrous metal in a highly heated condition.

8. The process of combining aluminum with ferrous metal, which consists in mixing pure aluminum with fire clay in the proportions of about three parts aluminum to one part clay by volume, covering said mixture with additional clay in the proportions of four to five parts of clay by volume to one part of the mixture, heating the covered mixture to a temperature of 2000 F. to 2200 F. for about 30 minutes, allowing the temperature to drop for about 15 minutes, re-

6 heating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, and then adding the pulverized aluminum mass to the ferrous metal in a highly heated condition.

9. The process of treating ferrous metal with aluminum which consists in covering pulverized pure aluminum with fire clay and heating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, spreading the pulverized aluminum mass over the bottom of a melting furnace, charging the ferrous metal on. top of said mass, and melting the charge and holding it at the melting temperature until the surface of the melt becomes quiescent.

10. The process of treating ferrous metal with aluminum which consists in mixing pulverized pure aluminum with a lesser amount of fire clay, covering the mixture with additional fire clay and heating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, spreading the pulverized aluminum mass over the bottom of a melting furnace, charging the ferrous metal on top of saidmass, and melting the charge and holding it at the melting temperature until the surface of the melt becomes quiescent.

11. The process of treating ferrous metal with aluminum which consists in covering pulverized pure aluminum with fire clay and heating to a temperature of 2000 F. to 2200 F., cooling and separating the resulting aluminum mass and pulverizing the same, spreading the pulverized aluminum mass over the bottom of a melting furnace, charging the ferrous metal on top of said mass, and melting the charge and holding it at the melting temperature for approximately thirty to sixty minutes.

12. The process of treating ferrous metal with aluminum which consists in mixing pulverized pure aluminum with a lesser amount of fire clay, covering the mixture with additional fire clay and heating to a temperature of 2000 F. to 2200 cooling and separating the resulting aluminum mass and pulverizing the same, spreading the pulverized aluminum mass over the bottom of a melting furnace, charging the ferrous metal on top of said mass, and melting the charge and holding it at the melting temperature for approximately thirty to sixty minutes.

GUY E. MCKINNEY. PAUL J. MOTTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 791,170 Vernon May 10', 1905 1,562,655 Pacz Nov. 24, 1925 1,775,339 De Vries Sept. 9, 1930 

1. THE PROCESS OF COMBININNG ALUMINUM WITH FERROUS METAL, WHICH CONSISTS IN COVERING PLUVERIZED PURE ALUMINUM WITH FIRE CLAY AND HEATING TO A TEMPERATURE OF 2000*F. TO 2200* F., COOLING AND SEPARATING THE RESULTINNG ALUMINUM MASS AND PULVERIZING THE SAME, AND THEN ADDING THE PULVERIZED ALUMINUM MASS TO THE FERROUS METAL IN A HIGHLY HEATED CONDITION. 